Defender split-screening

Sinistar

Member

Donor 2021, 2023
Joined
Mar 10, 2010
Messages
397
Reaction score
24
Location
Las Vegas, Nevada
***SOLVED!!!***

I have a Defender I've been restoring- had a ram issue when i got it. Last night replaced all the ram's with the newer type and fixed the ram issue.

So now it's booting up no problem, but the screen is split in half with identical images appearing on both the upper and lower half. The image appearing on both halves is of what would normally be the lower half of the screen.

When in test mode- I can see that the linearity is off on the test pattern as well. Though the monitor plays fine and only displays this error for the test pattern or actual game.

I am leaning toward the Monitor Sync Generator, but have no idea what to replace or look into on that.
 
Last edited:
Bump'd for searching for an hour and not finding too many similar issues.

Anyone have a lead on this? Is there anyway to adjust the screen from test mode?
 
I have a Defender I've been restoring- had a ram issue when i got it. Last night replaced all the ram's with the newer type and fixed the ram issue.

So now it's booting up no problem, but the screen is split in half with identical images appearing on both the upper and lower half. The image appearing on both halves is of what would normally be the lower half of the screen.

When in test mode- I can see that the linearity is off on the test pattern as well. Though the monitor plays fine and only displays this error for the test pattern or actual game.

I am leaning toward the Monitor Sync Generator, but have no idea what to replace or look into on that.

I say address generator circuit. Get a copy of the Williams logic probe debugging recap and pick up a decent logic probe off of 'da bay.

I have a Defender MPU for trade + $$ if you would prefer...

Saltbreez
 
Try pulling and cleaning the Video Decoder chips. I had the same problem and cleaning the ROMs and replacing them fixed it. No guarantees, but it is a start.

ken
 
Ah, thanks ken and Saltbreeze. Just somewhat a relief to find someone with a similar problem and a point in the right direction. Annoying are the issues where there's just no lead to follow. Gonna post some pics in a little while to go along with the problem.
 
Here are a couple of pics as to what is happening. I will keep on top of this and post whatever findings I can on this issue.

You can see that even in test pattern, the screen is divided evenly- with each half displaying what is normally the lower half.


REAL men play Defender with NO Radar!
 

Attachments

  • IMG00400.jpg
    IMG00400.jpg
    54.3 KB · Views: 10
  • IMG00396.jpg
    IMG00396.jpg
    46.4 KB · Views: 20
YellowDog nailed it! Thanks so much, man! Saltbreeze was all talkin logic probes and shit (scared me!), and a damn pencil eraser solved it! Amazing!

I couldn't believe it when I saw the screen fix, oxidation on the pins caused that?!

KLOVrs come through AGAIN!
 
Last edited:
It doesn't take much to cause a bad contact on a socket. ;)
 
Back
Top Bottom